engleski

BIOCHEMICAL, MICROSTRUCTURAL AND ANTIMICROBIAL CHARACTERIZATION OF BACTERIAL NANOCELLULOSE OBTAINED BY KOMBUCHA ROOIBOS TEA FERMENTATION

Kombucha is a traditional healthy beverage obtained as a final result after fermentation of sweetened tea by the compelling symbiosis of acetic acid bacteria and osmotolerant yeasts. Kombucha fermentation is, in general, initiated by yeast species, succeeded and dominated by acid-tolerant bacterial species. In this study, two goals have been set: a) the production of organic acids (acetic and gluconic), and b) the biosynthesis of bacterial nanocellulose by biotransformation of kombucha in Rooibos tea sweetened with sucrose (60, 80 and 100 g/L). Changes in pH were related to the symbiotic metabolic activities of yeasts and acetic acid bacteria, and it is decreased by the formation of organic acids. Analysing samples of bacterial nanocellulose by FT-IR spectroscopy, XRD analysis, and scanning electron microscopy (SEM), it was detected that the samples had a higher percentage of amorphous regions than crystalline regions, as it was expected. The thickness and yield of bacterial cellulose increased with fermentation time (12 days). Antimicrobial activities were observed in the fermented samples against the tested microorganisms (Salmonella typhimurium, Escherichia coli, and Pseudomonas sp.), but kombucha did not inhibit Vibrio cholerae. Results obtained from this study suggest that the yield of nanocellulose depends on many factors that need to be further optimized to achieve maximum yield. This work lays a foundation for using kombucha as a model system for microbial ecology.

Bacterial nanocellulose biosynthesis ; Kombucha tea fermentation ; Microbial ecology

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